Run test on macOS 14 with upstream clang

[burnpanck]

macOS 14 is the only platform that tests on arm64 on GitHub Actions (and is available for public repos). We already test on macOS 14, but so far only with Apple Clang. Apple Clang isn't a widely known compiler in terms of standards compliance, so test with upstream clang should be valuable. In particular, Apply Clang doesn't seem to warn about prevision loss from long to long double, but upstream clang does. Thus, with this PR, we actually detect the causes of issue #611. #611 is already fixed on master, so the (fast-forward) merge should fix the CI issues that will appear.

[mpusz]

Thanks! I have no working experience with Apple platforms, so your help here is greatly appreciated.

[mpusz]

It seems we have some runtime issues with precision on a new platform for some unit tests. Could you please fix it on your side as I have no way to repo this in my environment?

[burnpanck]

Yeah, I left those issues in on purpose, to highlight that these tests do in fact add value :-). I'll merge the current master, where the recently merged #612 (fix to #611) should resolve this issue.

[burnpanck]

Ah, here is now that small precision loss in the trigonometric functions due to long double being the same as double in this environment. I cherry-picked that fix from #615, increasing the threshold to two epsilon for those particular tests. Hopefully, now all is green again.

[mpusz]

Thanks!